Table operations

• A partitioned table can have a maximum of six levels of partitions.
• By default, a table can have a maximum of 60,000 partitions. You can adjust the maximum number of partitions in a table based on your business requirements.

-- Create a table. 
create table [if not exists] <table_name>
 [(<col_name> <data_type> [not null] [comment <col_comment>], ...)]
 [comment <table_comment>]
 [partitioned by (<col_name> <data_type> [comment <col_comment>], ...)]
 [lifecycle <days>];
-- Create a table based on an existing table. 
 create table [if not exists] <table_name> [as <select_statement> | like <existing_table_name>];

• if not exists: optional. If you create a table by using the name of an existing table but do not specify the if not exists parameter, an error is returned. If you create a table by using the name of an existing table and specify the if not exists parameter, a success message is returned even if the schema of the existing table is different from the schema of the table that you want to create. If you create a table by using the name of an existing table, the table is not created and the metadata of the existing table remains unchanged.
• table_name: required. The name of a table. The name must be 1 to 128 bytes in length, and can contain letters, digits, and underscores (_). The name must start with a letter and cannot contain special characters. The name is not case-sensitive. If the value of this parameter does not meet the requirements, an error is returned.
• col_name: optional. The name of a table column. The name must be 1 to 128 bytes in length, and can contain letters, digits, and underscores (_). The name must start with a letter and cannot contain special characters. The name is not case-sensitive. If the value of this parameter does not meet the requirements, an error is returned.
• col_comment: optional. The comment of a column. The comment must be a valid string that is 1 to 1,024 bytes in length. If the value of this parameter does not meet the requirements, an error is returned.
• table_comment: optional. The comment of a table. The comment must be a valid string that is 1 to 1,024 bytes in length. If the value of this parameter does not meet the requirements, an error is returned.
• data_type: optional. The data type of a column. The following data types are supported: BIGINT, DOUBLE, BOOLEAN, DATETIME, DECIMAL, and STRING. For more information about data types, see Data type editions.
• not null: optional. If you specify this parameter for a column, the values of the column cannot be NULL. For more information about how to modify the parameter, see Change the non-nullable property of a non-partition key column in a table.
• partitioned by (<col_name> <data_type> [comment <col_comment>], ...: optional. The partition fields of a partitioned table.
  • col_name: the name of a partition key column. The name must be 1 to 128 bytes in length, and can contain letters, digits, and underscores (_). The name must start with a letter and cannot contain special characters. The name is not case-sensitive. If the value of this parameter does not meet the requirements, an error is returned.
  • data_type: the data type of a partition key column. In MaxCompute V1.0 data type edition, partition key columns must be of the STRING type. In MaxCompute V2.0 data type edition, partition key columns can be of the TINYINT, SMALLINT, INT, BIGINT, VARCHAR, or STRING type. For more information, see Data type editions. If you use a partition field to partition a table, a full table scan is not required when you add partitions, update partition data, or read partition data. This improves the efficiency of data processing.
  • col_comment: the comment of a partition key column. The comment must be a valid string that is 1 to 1,024 bytes in length. If the value of this parameter does not meet the requirements, an error is returned.
  Note The value of a partition key column cannot contain double-byte characters, such as Chinese characters. It must start with a letter and can contain letters, digits, and supported special characters. It must be 1 to 128 bytes in length. The following special characters are supported: spaces, colons (:), underscores (_), dollar signs ($), number signs (#), periods (.), exclamation points (!), and at signs (@). The behavior of other characters is not defined, such as escaped characters \t, \n, and /.
• lifecycle: optional. The lifecycle of the table. The value must be a positive integer. Unit: days.
  • Non-partitioned tables: If data in a non-partitioned table remains unchanged for the number of days specified by days after the last data update, MaxCompute executes a statement, such as DROP TABLE, to reclaim the table.
  • Partitioned tables: MaxCompute determines whether to reclaim a partition based on the value of LastDataModifiedTime. Unlike non-partitioned tables, a partitioned table is not dropped even if all the partitions in the table are reclaimed. You can configure lifecycles for tables, but not for partitions.

• Example 1: Create a non-partitioned table named test1.

  create table test1 (key STRING);

• Example 2: Create a partitioned table named sale_detail.

  create table if not exists sale_detail(
   shop_name     STRING,
   customer_id   STRING,
   total_price   DOUBLE)
  partitioned by (sale_date STRING, region STRING); 

• Example 3: Create a table named test3 with a lifecycle.

  create table test3 (key BOOLEAN) partitioned by (pt STRING, ds STRING) lifecycle 100;

• Example 4: Create a table named test4 based on the test3 table. Make sure that all the properties, such as field type and partition type, of the test4 table except the lifecycle are the same as the properties of the test3 table.

  create table test4 like test3;

• Example 5: Create a table named test5 based on the test3 table and copy the data of the test3 table, except the lifecycle, to the test5 table.

  create table test5 AS select * from test3;

alter table <table_name> changeowner to <new_owner>;

• table_name: required. The name of the table whose owner you want to change.
• new_owner: required. The new owner of the table.

-- Change the owner of the test1 table to ALIYUN$xxx@aliyun.com. 
alter table test1 changeowner to 'ALIYUN$xxx@aliyun.com';

drop table [if exists] <table_name>; 

• if exists: optional. If you do not specify the if exists parameter and the table that you want to drop does not exist, an error is returned. If you specify the if exists parameter, a success message is returned regardless of whether the table exists.
• table_name: required. The name of the table that you want to drop.

-- Drop the sale_detail table. A success message is returned regardless of whether the sale_detail table exists. 
drop table if exists sale_detail; 

-- View the information about a table or view. 
desc <table_name|view_name>; 
-- View the information about an external table. 
desc extended <table_name>; 

• table_name: required. The name of the table that you want to view.
• view_name: required. The name of the view that you want to view.
• extended: the external table that you want to view. This parameter is required if the table that you want to view is an external table.

• Example 1: Query the information about the partitioned table sale_detail.

  desc sale_detail;               

  The following result is returned:

  +------------------------------------------------------------------------------------+
  | Owner: ALIYUN$****@aliyun.com | Project: test_project                              |
  | TableComment:                                                                      |
  +------------------------------------------------------------------------------------+
  | CreateTime:               2014-01-01 17:32:13                                      |
  | LastDDLTime:              2014-01-01 17:57:38                                      |
  | LastModifiedTime:         1970-01-01 08:00:00                                      |
  +------------------------------------------------------------------------------------+
  | InternalTable: YES      | Size: 0                                                  |
  +------------------------------------------------------------------------------------+
  | Native Columns:                                                                    |
  +------------------------------------------------------------------------------------+
  | Field           | Type       | Comment                                             |
  +------------------------------------------------------------------------------------+
  | shop_name       | string     |                                                     |
  | customer_id     | string     |                                                     |
  | total_price     | double     |                                                     |
  +------------------------------------------------------------------------------------+
  | Partition Columns:                                                                 |
  +------------------------------------------------------------------------------------+
  | sale_date       | string     |                                                     |
  | region          | string     |                                                     |
  +------------------------------------------------------------------------------------+

• Example 2: Query the information about the view sale_detail_view.

  desc sale_detail_view;

  The following result is returned:

  +------------------------------------------------------------------------------------+
  | Owner: ALIYUN$****@aliyun.com | Project: test_project                              |
  | TableComment: a view for table sale_detail                                         |
  +------------------------------------------------------------------------------------+
  | CreateTime:               2020-11-19 16:18:35                                      |
  | LastDDLTime:              2020-11-19 17:27:22                                      |
  | LastModifiedTime:         2020-11-19 16:18:35                                      |
  +------------------------------------------------------------------------------------+
  | VirtualView  : YES  | ViewText: select shop_name, customer_id, total_price from sale_detail |
  +------------------------------------------------------------------------------------+
  | Native Columns:                                                                    |
  +------------------------------------------------------------------------------------+
  | Field           | Type       | Label | Comment                                     |
  +------------------------------------------------------------------------------------+
  | store_name      | string     |       |                                             |
  | customer_id     | string     |       |                                             |
  | price           | double     |       |                                             |
  +------------------------------------------------------------------------------------+
  
  OK

desc <table_name> partition (<pt_spec>);

• table_name: required. The name of the partitioned table whose partition information you want to view.
• pt_spec: required. The information about the partition that you want to view. The value of this parameter is in the partition_col1=col1_value1, partition_col2=col2_value1... format. If a table has multi-level partitions, you must specify the values of all the partition key columns.

-- Query information about the partitioned table sale_detail. 
desc sale_detail partition (sale_date='201310',region='beijing');

+------------------------------------------------------------------------------------+
| PartitionSize: 2109112                                                             |
+------------------------------------------------------------------------------------+
| CreateTime:               2015-10-10 08:48:48                                      |
| LastDDLTime:              2015-10-10 08:48:48                                      |
| LastModifiedTime:         2015-10-11 01:33:35                                      |
+------------------------------------------------------------------------------------+
OK

-- Display all the tables and views in a project. 
show tables;
-- Display the tables or views whose names contain the chart keyword in a project. 
show tables like '<chart>';

-- Display the tables whose names contain the sale* keyword in a project. The asterisk (*) indicates any character. 
show tables like 'sale*';              

ALIYUN$account_name:sale_detail
......
-- ALIYUN is a system prompt, which indicates that the table is created by using an Alibaba Cloud account. If the table was created by a RAM user, the system prompt is RAM. 

show partitions <table_name>; 

table_name: required. The name of the partitioned table whose partition information you want to query.

-- Display all the partitions of the sale_detail table. 
show partitions sale_detail;

sale_date=201310/region=beijing
sale_date=201312/region=shenzhen
sale_date=201312/region=xian
sale_date=2014/region=shenzhen

OK